The invention relates to a capsule opening arrangement for a powder inhaler device according to the preamble of claim 1. In particular, the invention relates to a capsule severing arrangement.
Several types of powder inhaler devices are known in the prior art. One of these types is a device which uses capsules containing powder, said capsules needing to be opened before the device can be operated by a user.
Two main types of device are available for opening such capsules. The first is a pin arrangement within the inhaler device, said pin being operable so as to pierce a capsule and thus allow access to its contents. Such a device is known from U.S. Pat. No. 4 069 819 for example. Due to the presence of a reduced pressure around the powder capsule when a user inhales, and due to a processional motion of the capsule in a restricted cavity, the powder is withdrawn therefrom.
The second type of device for opening such capsules is a device which separates a two-part capsule into its two parts by first clamping one part and then forcing the other part away therefrom. An example of such a device is disclosed in WO-A-91/19524, said device corresponding to the features defined in the preamble of claim 1.
Such devices suffer from several disadvantages. The pin-piercing device produces a relatively small opening within the capsule and may thus lead to it not being completely emptied. Although the problem can be alleviated to some extent by providing multiple piercing elements, variations in the dose provided may still be observed.
The capsule-separation device relies on the capsule being of the separable type. Additionally, the separation of the capsules relies to a great extent on a good balance between capsule shell hardness and separation force required to separate the two parts. Moreover, even when separation is achieved, the loose parts are left to block the flow passage of the powder. Furthermore a grid structure is also required, on which powder may accumulate and cause blockage.
The present invention seeks to provide a solution to the aforementioned problems by means of a capsule opening arrangement having the features defined in appended claim 1.
Preferred features of the invention are defined in the dependent claims.
In a particularly preferred embodiment of the invention, the opening device is intended to be attached, or integral with, the powder inhaler of the type disclosed in WO-A95/03846. To avoid repetition of the principal of operation of such device, which will be clear to the skilled man upon reading said document, specific reference is hereby made to said document in its entirety.
Although the invention will be elucidated by reference to a particular form of a device of the type according to WOA-95/03846, it will be understood by the skilled man that the capsule opening device of the present invention will also be applicable to other forms of inhaler devices.